n8n-io/n8n · error · TreeRepositoryNotSupportedError

Tree repositories are not supported in ${driver.options.type

Error message

Tree repositories are not supported in ${driver.options.type} driver.

What it means

EntityManager.getTreeRepository checks the active driver's `treeSupport` flag (false for MongoDB and any driver without closure-table / nested-set support). When treeSupport is false, it throws TreeRepositoryNotSupportedError naming the driver type. Tree repositories require SQL features (CTEs/closure tables) that some drivers cannot provide.

Source

Thrown at packages/@n8n/typeorm/src/entity-manager/EntityManager.ts:1254

		// if repository was not found then create it, store its instance and return it
		const newRepository = new Repository<any>(target, this, this.queryRunner);
		this.repositories.set(target, newRepository);
		return newRepository;
	}

	/**
	 * Gets tree repository for the given entity class or name.
	 * If single database connection mode is used, then repository is obtained from the
	 * repository aggregator, where each repository is individually created for this entity manager.
	 * When single database connection is not used, repository is being obtained from the connection.
	 */
	getTreeRepository<Entity extends ObjectLiteral>(
		target: EntityTarget<Entity>,
	): TreeRepository<Entity> {
		// tree tables aren't supported by some drivers (mongodb)
		if (this.connection.driver.treeSupport === false)
			throw new TreeRepositoryNotSupportedError(this.connection.driver);

		// find already created repository instance and return it if found
		const repository = this.treeRepositories.find((repository) => repository.target === target);
		if (repository) return repository;

		// check if repository is real tree repository
		const newRepository = new TreeRepository(target, this, this.queryRunner);
		this.treeRepositories.push(newRepository);
		return newRepository;
	}

	/**
	 * Creates a new repository instance out of a given Repository and
	 * sets current EntityManager instance to it. Used to work with custom repositories
	 * in transactions.
	 */
	withRepository<Entity extends ObjectLiteral, R extends Repository<any>>(
		repository: R & Repository<Entity>,

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Use a tree-supporting driver (Postgres, MySQL, SQLite, MSSQL) for entities decorated with @Tree/@TreeChildren/@TreeParent.
2. If you must stay on MongoDB, model the hierarchy manually (parent references + recursive aggregation) and stop using the TreeRepository API.
3. Audit `@Tree(` decorators across the codebase before changing the configured driver.

Example fix

// before - tree entity used against MongoDB
@Entity()
@Tree('closure-table')
class Category { @TreeChildren() children?: Category[]; }
// DataSource type: 'mongodb'

// after - use Postgres, or drop tree decorators on Mongo
// Option A: switch datasource to a tree-supporting driver
const ds = new DataSource({ type: 'postgres', ... });
// Option B: keep Mongo, remove @Tree and model parent refs manually

function assertTreeSupported(driver: import('@n8n/typeorm').Driver): void {
  if ((driver as any).treeSupport === false) {
    throw new Error(`Driver ${driver.options.type} does not support tree repositories`);
  }
}
assertTreeSupported(connection.driver);
await manager.getTreeRepository(Category);

function driverSupportsTrees(driver: import('@n8n/typeorm').Driver): boolean {
  return (driver as any).treeSupport !== false;
}

When it happens

Trigger: Configuring a @TreeParen/TreeChildren/TreeLevelColumn entity against MongoDB; calling `manager.getTreeRepository(Category)` while connected to a non-tree-supporting driver; mixing a tree-decorated entity into a multi-DB project where one connection is MongoDB; migrating from SQL to Mongo without removing tree decorators.

Common situations: Switching DB engines without auditing entity decorators; copy-pasting a tree-structured entity from a SQL project into a Mongo project; testing against Mongo while production runs on Postgres.

Related errors

• Cannot attach entity "${entityName}" to its parent. Please m
• Nested sets do not support multiple root entities.
• Cannot save user <${this.email}>: Provided email is invalid
• Wrong driver: "${driverType}" given. Supported drivers are:
• Driver not Connected

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/84af38ced2ba3aef. Report an issue: GitHub.